Optical systems are widely used in communications applications to facilitate the exchange of information such as voice and data over fiber cable, which may be fabricated from glass or any other suitable composite material. Both telephony and Internet-based systems exploit the wide bandwidth and large data capacity that optical systems provide. Additionally, as compared to conventional wired systems, optical networks are easily maintained and repaired.
Conventional optical systems include a transmitter having a laser that operates at or near one of the wavelengths specified by the International Telecommunications Union (ITU). The laser could be an external cavity laser having an optical cavity, a grating, and an etalon. In such an arrangement, the grating coarsely tunes the laser and the etalon finely tunes the laser. As will be readily appreciated by those having ordinary skill in the art, the optical length of the cavity in which a laser operates and the free spectral ranges of the grating and the etalon affect the wavelength at which the laser lases. Accordingly, as the dimensions of the laser cavity change, the operating wavelength of the laser drifts, resulting in reduced power output from the laser and potentially in mode hopping of the laser. Additionally, it is possible to fabricate lasers capable of operation at a number of different wavelengths that are spaced evenly with respect to one another. For example, etalons have free spectral ranges of 25, 50, and 100 Gigahertz (GHz), which allow lasers to be designed to operate within these frequency spacings.
To address wavelength drift and to allow for wavelength tuning of lasers, gratings of previous external cavity lasers were pivotable about their axes. The pivotable nature of the gratings allowed the grating to steer a particular wavelength of interest so that it would be reflected from the grating at an angle that would cause the optical energy to reflect into the optical cavity for lasing.